<template>
  <div>
    <h1>当前求和为：{{sum}}</h1>
    <select v-model="n">
      <option :value="1">1</option>
      <option :value="2">2</option>
      <option :value="3">3</option>
    </select>
    <button @click="addition">+</button>
    <button @click="subtraction">-</button>
    <button @click="additionOdd">当前求和为奇数再加</button>
    <button @click="additionWait">等一等再加</button>
  </div>
</template>

<script>
export default {
    name:'Count',
    data(){
      return{
        n:1,
        sum:0
      }
    },
    methods:{
      addition(){
        this.sum += this.n;
      },
      subtraction(){
        this.sum -= this.n;
      },
      additionOdd(){
        if (this.sum%2) {
          this.sum += this.n
        }
      },
      additionWait(){
        setTimeout(() => {
          this.sum += this.n
        }, 500);
      }
    }
}
</script>

<style>
  button{
    margin-left: 5px;
  }
</style>